FWS & Partners Ensure Future of Rare Invertebrate
By: Jared Martin, USFWS Communications Contributor
If you happen to travel through central Nebraska, you may be lucky enough to encounter one of a newly discovered insect known only from the state. Amongst the ticks, poison ivy, and sulfur-smelling sloughs lives the Platte River caddisfly, (Ironoquia plattensis). Found in central Nebraska, this aquatic, moth-like insect inhabits backwater sloughs along the Platte, Loup and Elkhorn Rivers.
Prior to 1997, no one was aware of the Platte River caddisfly (PRC). In fact, the species was discovered incidentally during a field study at the Platte River Whooping Crane Maintenance Trust (Crane Trust) by biologists Matt Whiles and Beth Goldowitz.
“It was first noticed on land in buckets intended to capture amphibians and was a very abundant component of the slough at the Crane Trust,” writes Lindsay Vivian, a Nebraska-based biologist with the U.S. Fish and Wildlife Service’s (Service) Mountain-Prairie Region.
What makes the PRC unique to other Trichoptera, (caddisflies) is its peculiar aestivation (summer hibernation) period during its one-year lifecycle.
“While most caddisflies live in water through the time they emerge as adults, the PRC spends three months aestivating on land before it emerges as an adult in the autumn,” writes Vivian. “The Platte River caddisfly aestivates along slough banks in moist, shaded areas, or underground against plant roots. The terrestrial life stage in the PRC is thought to be an adaptation to avoid the stress of summer dry periods that occur in prairie systems."
Since the species’ discovery, a number of partnering organizations have worked to conduct surveys for additional PRC populations to gain a better understanding of the small insect’s range. Goldowitz, who at the time was with the Nebraska Game and Parks Commission (NGPC), conducted surveys along the Platte and Loup Rivers in 1999 and 2004. Out of 48 sites visited, she found the caddisfly at nine sites along a 100 kilometer (60-mile) span of the Platte River.
In the fall 2004, the caddisfly was not found at the Crane Trust, likely due to drought. Because of its apparent rarity, the NGPC designated the caddisfly a Tier 1 species in 2005. According to the State’s natural legacy plan, Tier 1 species are those most at risk of extinction on a global scale or in Nebraska. In 2007, the species was found to be extirpated from one other site near Shelton, Nebraska. Because of concern over its decline, the Service enlisted the help of the University of Nebraska at Kearney (UNK) to conduct more thorough searches for the caddisfly in Nebraska. Between 2009 and 2011, the caddisfly was documented at 30 new sites along the Platte, Loup, and Elkhorn Rivers. Most sites were discovered by Vivian, formerly of the UNK. Her efforts were supported by biologists from the Nebraska Public Power District, the Central Nebraska Public Power and Irrigation District, Central Nebraska Natural Resources District, the Headwaters Corporation, NGPC, and the Nature Conservancy. In addition, one site was discovered by biologists from the Crane Trust.
In 2011 and 2012, the Service assessed whether the Platte River caddisfly was warranted for protection under the Endangered Species Act. The 12-month finding concludes that the PRC currently inhabits a much larger area than previously believed. Additionally, using aerial imagery, potentially suitable habitat has been identified along other rivers in Nebraska, such as the Niobrara River.
Within the assessment, the Service analyzed potential threats facing the caddisfly and indicated that these stressors across the landscape are not currently threatening the caddisfly with extinction. Threats analyzed included:Â water impoundments and diversions for agriculture, drought, bank stabilization projects, invasive species, cattle grazing, pesticides, and climate change. In the finding, the Service also evaluated the presence of various conservation programs along Nebraska’s rivers and their potential impact on the caddisfly.
Several programs and regulations have also been set forth by State and Federal agencies and non-governmental organizations that will provide protection for the insect now and into the future. These efforts primarily include protecting river flows and groundwater levels by limiting the amount of water development that can occur. Current data also indicates that a majority of the species’ populations inhabit protected environments. Around 60 percent of known PRC populations are located on lands managed by conservation groups, which are protected from future land development. Other groups such as the Service’s Partners for Fish and Wildlife Program and the Nature Conservancy are restoring wetlands across the state of Nebraska, which provides more protection to the species. With these efforts in place and the species’ apparent success in maintaining secure population numbers, the future of the Platte River caddisfly appears to be in good hands.